Elastic support device and power steering device

ABSTRACT

An elastic support device ( 70 ) has a vibration reduction member ( 35 ) for supporting a vibration transmission medium ( 34 ). The vibration transmission medium ( 34 ) is connected to the vibration reduction member ( 35 ) by a connection member ( 42 ). The vibration reduction member ( 35 ) includes a sleeve ( 43 ) made from a rigid body, through which sleeve the connection member ( 42 ) is inserted, and an elastic member ( 45 ) surrounding an outer periphery of the sleeve ( 43 ). The elastic member ( 45 ) includes a tubular body ( 49 ) firmly fixed on an outer peripheral surface ( 44 ) of the sleeve ( 43 ) and an annular plate portion ( 50 ) projecting radially outward of the body ( 49 ). A fitting groove ( 58 ) of an outer peripheral edge portion ( 57 ) of the annular plate portion ( 50 ) is fitted on a peripheral edge ( 60 ) of an installation hole ( 59 ). A first and a second face ( 52, 53 ) of the annular plate portion ( 50 ) include recesses ( 54, 55 ), respectively. In the annular plate portion ( 50 ), a thin-walled portion ( 56 ) corresponding to a portion between bottoms of the recesses ( 54, 55 ) of the first and the second faces ( 52, 53 ) is formed.

TECHNICAL FIELD

The present invention relates to an elastic support device and a powersteering apparatus.

BACKGROUND ART

Automobiles comprise various types of devices such as engines andsteering devices, and the devices include devices mounted on the vehiclebodies (bodies) with brackets serving as mounting members sandwichedtherebetween.

For example, an automobile disclosed in Japanese Unexamined PatentPublication No. 11-334616, A laid open to public inspection withnon-examination by Japanese Patent Office on Dec. 7, 1999 comprises anelectric motor-driven pump type power steering apparatus. The electricmotor-driven pump type power steering apparatus drives a pump using anelectric motor, and supplies hydraulic oil stored in a tank or the liketo a power cylinder coupled to a steering mechanism to produce asteering assist force. The electric motor, the pump, the tank, and thelike are mounted on a vehicle body with a fixing member sandwichedtherebetween.

Generally, the electric motor and the pump generate vibration at thetime of driving. The vibration generated by the pump is also transmittedto the tank connected to the pump. When the electric motor, the pump,and the tank are mounted on the vehicle body with only a bracketsandwiched therebetween, therefore, the vibration is transmitted to thevehicle body, causing noise in the vehicle body.

The same problems also exist in not only the electric motor, the tank,and the pump but also other devices mounted on the vehicle body.

An object of the present invention is to provide a low-cost elasticsupport device capable of reducing vibration and noise in a vehicle bodyand satisfactorily maintaining a vibration absorbing effect for a longtime period and a power steering apparatus comprising the same.

DISCLOSURE OF INVENTION

In order to attain the above-mentioned object, in one mode of thepresent invention, an elastic support device that elastically supports avibration transmission medium comprises an installation hole provided ina fixing member, and a vibration reduction member mounted on theinstallation hole for supporting the vibration transmission medium, thevibration reduction member comprising a sleeve composed of a rigid bodyhaving a mounting bolt insertion hole and mounted on the vibrationtransmission medium by a mounting bolt inserted through the mountingbolt insertion hole, and an elastic member surrounding an outerperipheral surface of the sleeve, the elastic member comprising atubular body fastened to the outer peripheral surface of the sleeve andan annular plate portion projecting radially outward from the body, theannular plate portion comprising first and second faces opposed to eachother in an axial direction of the annular plate portion and an outerperipheral edge, the outer peripheral edge of the annular plate portionincluding an annular fitting groove that can be fitted in a peripheraledge of the installation hole in the fixing member, the first and secondfaces of the annular plate portion respectively comprising recesses, theannular plate portion forming a thin-walled portion corresponding to anarea between a bottom of the recess in the first face and a bottom ofthe recess in the second face.

According to this mode, it is possible to satisfactorily make theelastic member flex by forming the recess and to sufficiently absorbvibration from the vibration transmission medium. Consequently,vibration and noise in a vehicle body can be significantly reduced byrestraining the transmission of the vibration to the vehicle bodythrough the fixing member. Further, the elastic member may be onlyprovided with the recess, resulting in low cost.

Since the body of the elastic member is fastened to the sleeve, the bodyof the elastic member can be prevented from being scraped against andseparated from the sleeve by the vibration from the vibrationtransmission medium, for example. Consequently, the elastic member canbe prevented from being damaged and slipping off the sleeve, so that avibration absorbing effect can be satisfactorily maintained for a longtime period.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view showing the schematic configuration of apower steering apparatus according to an embodiment of the presentinvention.

FIG. 2 is a schematic partial side view of a housing, a vibrationabsorbing member and a bracket.

FIG. 3 is a cross-sectional view taken along a line II-II shown in FIG.2.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the present invention will be described whilereferring to the accompanying drawings.

FIG. 1 is a schematic view showing the schematic configuration of apower steering apparatus 1 according to an embodiment of the presentinvention. Referring to FIG. 1, the power steering apparatus 1 comprisesa steering member 2 such as a steering wheel operated by a driver, asteering shaft 3 connected to the steering member 2, a pinion shaft 5connected to the steering shaft 3 through an intermediate shaft 4, and arack shaft 8 having a rack 7 meshed with a pinion 6 provided in thepinion shaft 5 and extending along the width of a vehicle.

To a pair of ends of the rack shaft 8, knuckle arms 10 for supportingcorresponding wheels 9 are respectively connected through correspondingtie rods 11. By the above-mentioned configuration, when the steeringmember 2 is operated so that the steering shaft 3 is rotated, therotation is transmitted to the pinion shaft 5 through the intermediateshaft 4 et al. The rotation of the pinion shaft 5 is converted intolinear motion of the rack shaft 8 arranged along the width of thevehicle by the pinion 6 and the rack 7. As a result, the knuckle arm 10is rotated, thereby achieving steering of the wheels 9.

A torsion bar 12 causing twisting depending on the direction and themagnitude of steering torque applied to the steering member 2 and ahydraulic control valve 13 whose opening changes depending on thedirection and the magnitude of the twisting of the torsion bar 12 areinterposed in a halfway portion of the steering shaft 3.

The hydraulic control valve 13 comprises four ports 14 to 17. Hydraulicoil pumped out of a tank 18 through an oil pipe 65 is supplied to theport 14 through an oil pipe 21 by a pump 20 interposed between the tank18 and a power cylinder 19 for generating a steering assist force. Theport 15 communicates with the tank 18 with an oil pipe 22 sandwichedtherebetween.

The ports 16 and 17 respectively communicate with oil chambers 25 and 26in the power cylinder 19 through oil pipes and 24. The oil chambers 25and 26 in the power cylinder 19 are respectively provided with pistons27 that are moved along the width of the vehicle by the difference inhydraulic pressure between the oil chambers 25 and 26. The piston 27 isconstructed integrally with the rack shaft 8.

When the steering member 2 is operated to rotate in any one of rotationdirections, the torsion bar 12 is twisted, so that hydraulic oil issupplied to either one of the oil chambers 25 and 26 in the powercylinder 19 from the hydraulic control valve 13 depending on an amountcorresponding to the twisting of the torsion bar 12. As a result, thedifference in hydraulic pressure occurs between the oil chambers 25 and26, and the piston 27 in the power cylinder 19 is moved depending on thedifference in hydraulic pressure, so that a steering assist force isapplied to the rack shaft 8.

In this case, an excess of hydraulic oil is returned to the tank 18 fromthe hydraulic control valve 13 through the oil pipe 22. When the torsionbar 12 is hardly twisted, the hydraulic control valve 13 enters anequilibrium state, where hydraulic oil supplied to the hydraulic controlvalve 13 from the pump 20 is returned to the tank 18 through the oilpipe 22 without being supplied to the power cylinder 19.

The pump 20 is, for example, a gear pump performing a pump function bythe rotation of a driving gear and a driven gear (not shown). An output(torque) of an electric motor 28 for pump driving is inputted to thedriving gear.

The electric motor 28 is driven and controlled by a controller 29including a microcomputer. Output signals of a steering angle sensor 30in the steering member 2, a vehicle speed sensor 31 for detecting thevehicle speed of a vehicle, a motor current detection circuit 32 fordetecting a current (a motor current) flowing in the electric motor 28,and a motor rotation speed sensor 33 for detecting the rotation speed ofthe electric motor 28 are fed to the controller 29.

The controller 29 controls the driving of the electric motor 28 so as toapply a suitable steering assist force corresponding to a steeringamount of the steering member 2 to the rack shaft 8 on the basis of thesignals fed from the steering angle sensor 30, the vehicle speed sensor31, the motor current detection circuit 32, the motor rotation speedsensor 33, and so forth.

A housing 34 of the electric motor 28 and the pump 20 integrallyconstitute a member to be mounted, for example. The housing 34 ismounted on a bracket 36 serving as a fixing member fixed to a vehiclebody 37 and elastically supported thereon by a pair of elastic supportdevices 70, for example. The housing 34 serves as a vibrationtransmission medium for transmitting vibration in rotating portions ofthe electric motor 28 and the pump 20 to the vehicle body 37. Theelastic support device 70 serves to reduce vibration transmission fromthe housing 34 to the vehicle body 37.

Referring to FIG. 2, the bracket 36 is formed in a plate shape by asteel plate, for example, and is arranged between the housing 34 and thevehicle body 37 indicated by a two-dot and dash line. The bracket 36 hasan opposite surface 38 opposed to the vehicle body 37, and is formedsuch that two bolts 39, for example, project from the opposite surface38. Each of the bolts 39 is inserted through a corresponding boltinsertion hole of the vehicle body 37, and is coupled to a correspondingnut 40.

Each of the elastic support devices 70 comprises a vibration reductionmember 35 mounted on the bracket 36 and a bolt 42 for mounting thevibration reduction member 35 in a state where it abuts against a seat41 provided in the housing 34.

FIG. 3 is a cross-sectional view taken along a line II-II shown in FIG.2. Referring to FIG. 3, the vibration reduction member 35 comprises asleeve 43 composed of a rigid body mounted on the seat 41 in the housing34 through a bolt 42 to be inserted, and an elastic member 45 fastenedto an outer peripheral surface 44 of the sleeve 43.

The sleeve 43 comprises first and second ends 43 a and 43 b. An annularflange 48 extending radially outward from the first end 43 a is providedat the first end 43 a of the sleeve 43. A first face 48 a of the flange48 abuts against a seat face 47 of the seat 41 in the housing 34, andreceives the seat face 47. The flange 48 allows a contact area with theseat face 47 of the housing 34 to be made larger. As a result, at thetime of fastening the bolt 42, a force per unit area which the seat face47 receives from the sleeve 43 can be reduced. Even when the housing 34is formed of aluminum or the like having relatively low mechanicalstrength, therefore, the seat face 47 is prevented from subsiding as theseat 41 is deformed.

The elastic member 45 is formed of synthetic rubber such as naturalrubber or nitrile rubber, for example. The elastic member 45 comprises atubular body 49 fastened to the outer peripheral surface of the sleeve43 and an annular plate portion 50 projecting radially outward from anintermediate portion in the axial direction of the body 49.

The body 49 in the elastic member 45 surrounds the sleeve 43. The body49 has a fastening surface fastened to the outer peripheral surface 44of the sleeve 43 and the second face 48 b of the flange 48 byvulcanizing adhesion, for example.

The annular plate portion 50 is formed integrally with the body 49 by asingle member, to surround the outer periphery of the body 49. Theannular plate portion 50 comprises first and second faces 52 and 53opposed to each other in the axial direction, and the first and secondfaces 52 and 53 are respectively formed with first and second recesses54 and 55 each having a V-shape in cross section.

The recesses 54 and 55 are respectively formed over the wholeperipheries, for example, of the corresponding faces 52 and 53. Byforming the recesses 54 and 55, a thin-walled portion 56 is formed in anintermediate portion in the radial direction of the annular plateportion 50. This makes the movement of the body 49 relative to theannular plate portion 50 easy.

Ease of elastic deformation of the elastic member 45 can be easily setby suitably setting the thickness Al of the thin-walled portion 56.Although the respective shapes of the recesses 54 and 55 differ in FIG.3, they may have the same shape.

An annular fitting groove 58 is provided in an intermediate portion inthe axial direction of an outer peripheral edge 57 of the annular plateportion 50. A peripheral edge 60 of an installation hole 59 in thebracket 36 is elastically fitted in the fitting groove 58. In a freestate where the vibration reduction member 35 is not mounted on thebracket 36, the diameter of a bottom surface 61 of the fitting groove 58is set at a value larger than the diameter of the installation hole 59in the bracket 36.

When the fitting groove 58 is fitted in the peripheral edge 60 of theinstallation hole 59 in the bracket 36, therefore, the annular plateportion 50 can be brought into press contact with the installation hole59 and reliably fixed thereto. Consequently, the annular plate portion50 can be prevented from being scraped against the installation hole 59in the bracket 36 to be damaged and being separated therefrom.

An outer peripheral surface 80 of the annular plate portion 50 has firstand second portions 81 and 82 with the fitting groove 58 interposedtherebetween, and the diameter of the first portion 81 is set at a valuesmaller than the diameter of the second portion 82. Consequently, theelastic member 45 is easily fitted in the installation hole 59 in thebracket 36.

An annular rim 62 is provided at the peripheral edge 60 of theinstallation hole 59 in the bracket 36. The rim 62 is formed by foldingthe peripheral edge 60 of the installation hole 59 in the bracket 36,for example. Further, a peripheral surface of the installation hole 59is formed so as to be coplanar in the axial direction. By theabove-mentioned configuration, the length B1 of the installation hole59, that is, the width in which the bracket 36 supports the elasticmember 45 is made larger.

The thickness C1 of the bracket 36 is so set that it can ensure strengthrequired to support the housing 34 and has such a natural frequency thatthe bracket 36 does not resonate upon receipt of vibration in thehousing 34. A washer 63 is arranged at the other end in the axialdirection of the sleeve 43 in the vibration reduction member 35, and isfastened to the body 49 in the elastic member 45 by vulcanizingadhesion, for example. The bolt 42 is inserted through the washer 63 andthe sleeve 43, and is screwed into a bolt hole 64 in the washer 41 inthe housing 34 and coupled thereto, to fasten the vibration reductionmember 35 to the washer 41 in the housing 34.

The elastic member 45 is mounted such that the first and second faces 52and 53 of the annular plate portion 50 are directed transversely (towardthe right to left in FIG. 3), that is, the own weight of the housing 34is exerted along the radius of the annular plate portion 50 in theelastic member 45.

According to the present embodiment, the recesses 54 and 55 are thusformed, thereby allowing the elastic member 45 to be satisfactorily madeflex so that the vibration in the housing 34 caused by the driving ofthe electric motor 28 and the pump 20 can be sufficiently absorbed.Consequently, vibration and noise in the vehicle body 37 can besignificantly reduced by satisfactorily preventing transmission of thevibration to the vehicle body 37.

Furthermore, the vibration absorbing effect is obtained only byproviding the elastic member 45 with the recesses 54 and 55, resultingin low cost. Further, the elastic member 45 and the sleeve 43 arefastened to each other. Therefore, the elastic member 45 can beprevented from being scraped against and separated from the sleeve 43 bythe vibration in the housing 34, for example. Consequently, the elasticmember 45 can be prevented from being damaged and slipping off thesleeve 43, thereby making it possible to satisfactorily maintain thevibration absorbing effect for a long time period.

The length B1 of the installation hole 59, that is, the width in whichthe bracket 36 supports the elastic member 45 can be sufficientlyensured by providing the rim 62 at the peripheral edge 60 of theinstallation hole 59 in the bracket 36, so that the elastic member 45can be satisfactorily supported.

The thickness C1 of the bracket 36 can be made as small as aboutone-half the conventional thickness, for example, without reducing thewidth in which the bracket 36 supports the elastic member 45, therebymaking it possible to significantly make the bracket 36 lightweight. Thebracket 36 can be molded by a smaller-sized pressing machine by furtherthin-walling the bracket 36, thereby making it possible to significantlyreduce the manufacturing cost.

The vibration and the noise in the vehicle body 37 can be reduced at lowcost without changing the electric motor 28 and the pump 20 each servingas a vibration source.

Since the annular elastic member 45 is transversely arranged, and theperipheral edge of the annular plate 50 in the elastic member 45 isengaged with the bracket 36, the elastic member 45 can perform a highvibration absorbing effect with respect to all vibrations in everyradial direction R1 of the annular plate portion 50. Further, a highvibration absorbing effect can be also performed with respect tovibrations in an axial direction Z1 of the annular plate portion 50.

The present invention is not limited to the above-mentioned embodiments.For example, the recesses 54 and 55 may be provided in only a part inthe circumferential direction of the annular plate portion 50 in theelastic member 45. Further, the vibration reduction member 35 may beinterposed between the bracket 36 and the vehicle body 37.

Furthermore, the tank 18 may be supported with the vibration reductionmember 35 interposed between a bracket (not shown) for supporting ahousing portion of the tank 18 and the vehicle body 37. In this case,the vibration generated by the pump 20 that is transmitted to the tank18 through the oil pipe 65 can be satisfactorily prevented from beingtransmitted to the vehicle body 37.

The present invention is not limited to a configuration in which ahousing of the electric motor and a housing of the pump that areintegrally constructed are supported. However, the present invention maybe a configuration in which the housing of the electric motor and thehousing of the pump that are independently constructed are respectivelysupported.

Alternatively, the elastic support device according to the presentinvention is applicable to support of another device, which is mountedon a vehicle body, other than an electric motor-driven pump type powersteering apparatus.

While the present invention has been described in detail by way of thespecific embodiments, those skilled in the art who have understood theforegoing contents would easily consider its changes, modifications, andequivalents of the embodiments. Therefore, the scope of the presentinvention should be defined by the claims and their equivalents.

The present application corresponds to an application No. 2003-153177filed with the Japanese Patent Office on May 29, 2003, the disclosure ofwhich is herein incorporated by reference.

1. An elastic support device that elastically supports a vibrationtransmission medium, comprising: an installation hole provided in afixing member fixed to a vehicle body; a vibration reduction membermounted on the installation hole for supporting the vibrationtransmission medium; and a connection member for connecting thevibration transmission medium to the vibration reduction member, thevibration reduction member comprising: a sleeve composed of a rigid bodythrough which the connection member is inserted; and an elastic membersurrounding an outer peripheral surface of the sleeve, the elasticmember comprising a tubular body fastened to the outer peripheralsurface of the sleeve and an annular plate portion projecting radiallyoutward from the body, the annular plate portion comprising first andsecond faces opposed to each other in an axial direction of the annularplate portion and an outer peripheral edge, the outer peripheral edge ofthe annular plate portion comprising an annular fitting groove fitted ina peripheral edge of the installation hole in the fixing member, thefirst and second faces of the annular plate portion respectivelycomprising recesses, and the annular plate portion forming a thin-walledportion corresponding to an area between a bottom of the recess in thefirst face and a bottom of the recess in the second face.
 2. The elasticsupport device according to claim 1, wherein at least one of the recessin the first face of the annular plate portion and the recess in thesecond face thereof has an annular shape.
 3. The elastic support deviceaccording to claim 1, wherein at least one of the recess in the firstface of the annular plate portion and the recess in the second facethereof includes a recess having a V shape in cross section.
 4. Theelastic support device according to claim 1, wherein the first face ofthe annular plate portion is opposed to the vibration transmissionmember, the recess in the first face has a V shape in cross section, andthe bottom of the recess in the first face is arranged so as to beoverlapped with the peripheral edge of the installation hole in theaxial direction of the annular plate portion.
 5. The elastic supportdevice according to claim 1, wherein the sleeve comprises first andsecond ends, the first end of the sleeve receiving a seat face providedin the vibration transmission medium.
 6. The elastic support deviceaccording to claim 5, wherein an annular flange extending radiallyoutward and receiving the seat face of the vibration transmission mediumis formed at the first end of the sleeve.
 7. The elastic support deviceaccording to claim 6, wherein the vibration transmission medium includesaluminum.
 8. The elastic support device according to claim 1, whereinthe annular plate portion is arranged at a position corresponding to anintermediate portion in an axial direction of the body.
 9. The elasticsupport device according to claim 1, wherein the bottom of the annulargroove is elastically compressed by the peripheral edge of theinstallation hole.
 10. The elastic support device according to claim 9,wherein a rim is provided at the peripheral edge of the installationhole.
 11. The elastic support device according to claim 1, wherein theelastic member includes rubber adhered by vulcanization to the outerperipheral surface of the sleeve.
 12. The elastic support deviceaccording to claim 1, wherein the connection member includes a screwmember, and the screw member is coupled to a screw hole provided in thevibration transmission medium through an insertion hole of the sleeve.13. The elastic support device according to claim 1, wherein the fixingmember comprises a bracket fixed to the vehicle body.
 14. A powersteering apparatus comprising: a power cylinder for generating asteering assist force; a tank storing hydraulic oil; a pump interposedbetween the tank and the power cylinder; an electric motor for drivingthe pump; a fixing member fixed to the vehicle body; a vibrationtransmission medium including at least one of a housing of the pump anda housing of the tank; and an elastic support device for elasticallysupporting the vibration transmission medium, the elastic support devicecomprising: an installation hole provided in the fixing member fixed toa vehicle body; a vibration reduction member mounted on the installationhole for supporting the vibration transmission medium; and a connectionmember for connecting the vibration transmission medium to the vibrationreduction member, the vibration reduction member comprising: a sleevecomposed of a rigid body through which the connection member isinserted; and an elastic member surrounding an outer peripheral surfaceof the sleeve, the elastic member comprising a tubular body fastened tothe outer peripheral surface of the sleeve and an annular plate portionprojecting radially outward from the body, the annular plate portioncomprising first and second faces opposed to each other in an axialdirection of the annular plate portion and an outer peripheral edge, theouter peripheral edge of the annular plate portion comprising an annularfitting groove that can be fitted in the peripheral edge of theinstallation hole in the fixing member, the first and second faces ofthe annular plate portion respectively comprising recesses, the annularplate portion forming a thin-walled portion corresponding to an areabetween the bottom of the recess in the first face and the bottom of therecess in the second face.
 15. The power steering apparatus according toclaim 14, wherein at least one of the recess in the first face of theannular plate portion and the recess in the second face thereof has anannular shape.
 16. The power steering apparatus according to claim 14,wherein at least one of the recess in the first face of the annularplate portion and the recess in the second face thereof includes arecess having a V shape in cross section.
 17. The power steeringapparatus according to claim 14, wherein the first face of the annularplate portion is opposed to the vibration transmission member, therecess in the first face thereof has a V shape in cross section, and thebottom of the recess in the first face is arranged so as to beoverlapped with the peripheral edge of the installation hole in theaxial direction of the annular plate portion.